Coat and claws as new matrices for noninvasive long-term cortisol assessment in dogs from birth up to 30 days of age

The last stage of fetal development and the neonatal period represent the most critical phases for the mammals' offspring. In the dog, the knowledge about the final intrauterine fetal development and biology, as well as about the neonatal physiology, remains scarce. Hormonal changes occurring in the last intrauterine fetal phase and during the early neonatal age are still not completely clear, probably because of the invasiveness related to the collection of the more common biological matrix, represented by circulating blood. Toward term of pregnancy, during parturition, and after birth, the hypothalamic-pituitary-adrenal axis is a key system regulating several physiological processes, and its activity was previously investigated by blood analysis, considered an invasive procedure providing a single-point measurement. In respect to animal welfare, and for a more correct long-term retrospective investigation, noninvasive hormonal studies were performed firstly on the hair of humans and coat of animals and, more recently, in the nails of human beings. This study was aimed to assess cortisol (CUR) in coat and claws of newborn puppies and to evaluate the possible influence of the newborn gender, breed body size, and age on coat and claws CUR concentrations. The results obtained from 165 newborn puppies evidenced that coat and claws CUR levels were highly correlated each other (P < 0.0001), although the CUR accumulation in the two matrices was different in relation to the class of age. Moreover, the puppies age influenced both coat and claws CUR concentrations (P < 0.05), with premature puppies showing higher values when compared to term born-dead puppies or puppies dead between 1 and 30 days of age. The present study reported that CUR is quantifiable in coat and claws of newborn dogs. Moreover, both matrices appear as useful tools for new, noninvasive, long-term perinatal and neonatal researches also in canine species.